The Centris 610 and 650 were replaced about six months after their introduction by the Quadra 610 and 650 models, which kept the same case and designs but raised the CPU speeds from 20 MHz and 25 MHz to 25 MHz and 33 MHz respectively; while the Centris 660AV was renamed to Quadra 660AV without any actual design change. These Macs also existed during Apple's transition from auto-inject floppy drives to manual-inject drives.[4] This is why there are two different styles of floppy drive bezel (faceplate) on these models. Some later Centris 660AV Macs have manual-inject floppy drives, so this change was not exactly concurrent with the name change.